Single damascene is an interconnection fabrication process for integrated circuits in which grooves are formed in an insulating layer and filled with a conductive material to form interconnects. Dual damascene is a multi-level interconnection process in which, in addition to forming the grooves of single damascene, conductive contact (or via) openings are also formed in the insulating layer. A conductive material is formed in the grooves and conductive contact (or via) openings.
In one standard dual damascene process, a first oxide layer is deposited over a conductive structure. A hard mask is formed over the first oxide layer and a first patterned photoresist layer is formed on the hard mask. The hard mask is patterned using the first photoresist layer as a pattern. The first photoresist layer is removed and a second oxide layer is then formed over the hard mask.
A second patterned photoresist layer is formed over the second oxide layer. Both the first oxide layer and the second oxide layer are etched to form the dual damascene opening. The first oxide layer is etched using the hard mask as a pattern and the underlying conductive structure as an etch stop. The second oxide layer is etched using the second photoresist layer as a pattern and the hard mask as an etch stop. The second photoresist layer is then stripped.
This process involves a combination of different steps to form the dual damascene structure. For example, the hardmask is patterned prior to forming the second dielectric layer. Thus, the partially fabricated integrated circuit is transferred between different processing systems to perform the different deposition and patterning steps.
In another dual damascene process, a dielectric is formed and patterned using a first photoresist. The first photoresist is removed and the dielectric is patterned again using a second photoresist. The vias and grooves are formed using the different patterning steps. This process uses a timed etch to control the depth of the grooves. This process is difficult to control. Thus, it is desirable to develop a process that reduces the complexity of the process to form a dual damascene structure.